Page and Brin founded Google in 1998.[23] Google attracted a loyal following among the growing number of Internet users, who liked its simple design.[24] Off-page factors (such as PageRank and hyperlink analysis) were considered as well as on-page factors (such as keyword frequency, meta tags, headings, links and site structure) to enable Google to avoid the kind of manipulation seen in search engines that only considered on-page factors for their rankings. Although PageRank was more difficult to game, webmasters had already developed link building tools and schemes to influence the Inktomi search engine, and these methods proved similarly applicable to gaming PageRank. Many sites focused on exchanging, buying, and selling links, often on a massive scale. Some of these schemes, or link farms, involved the creation of thousands of sites for the sole purpose of link spamming.[25]
SEO is not an appropriate strategy for every website, and other Internet marketing strategies can be more effective, such as paid advertising through pay per click (PPC) campaigns, depending on the site operator's goals. Search engine marketing (SEM) is the practice of designing, running and optimizing search engine ad campaigns.[56] Its difference from SEO is most simply depicted as the difference between paid and unpaid priority ranking in search results. Its purpose regards prominence more so than relevance; website developers should regard SEM with the utmost importance with consideration to visibility as most navigate to the primary listings of their search.[57] A successful Internet marketing campaign may also depend upon building high quality web pages to engage and persuade, setting up analytics programs to enable site owners to measure results, and improving a site's conversion rate.[58] In November 2015, Google released a full 160 page version of its Search Quality Rating Guidelines to the public,[59] which revealed a shift in their focus towards "usefulness" and mobile search. In recent years the mobile market has exploded, overtaking the use of desktops, as shown in by StatCounter in October 2016 where they analyzed 2.5 million websites and found that 51.3% of the pages were loaded by a mobile device [60]. Google has been one of the companies that are utilizing the popularity of mobile usage by encouraging websites to use their Google Search Console, the Mobile-Friendly Test, which allows companies to measure up their website to the search engine results and how user-friendly it is.

Optimization techniques are highly tuned to the dominant search engines in the target market. The search engines' market shares vary from market to market, as does competition. In 2003, Danny Sullivan stated that Google represented about 75% of all searches.[64] In markets outside the United States, Google's share is often larger, and Google remains the dominant search engine worldwide as of 2007.[65] As of 2006, Google had an 85–90% market share in Germany.[66] While there were hundreds of SEO firms in the US at that time, there were only about five in Germany.[66] As of June 2008, the market share of Google in the UK was close to 90% according to Hitwise.[67] That market share is achieved in a number of countries.

Engagement – Google is increasingly weighting engagement and user experience metrics more heavily. You can impact this by making sure your content answers the questions searchers are asking so that they’re likely to stay on your page and engage with your content. Make sure your pages load quickly and don’t have design elements (such as overly aggressive ads above the content) that would be likely to turn searchers off and send them away.

“Sharability” – Not every single piece of content on your site will be linked to and shared hundreds of times. But in the same way you want to be careful of not rolling out large quantities of pages that have thin content, you want to consider who would be likely to share and link to new pages you’re creating on your site before you roll them out. Having large quantities of pages that aren’t likely to be shared or linked to doesn’t position those pages to rank well in search results, and doesn’t help to create a good picture of your site as a whole for search engines, either.
Some search engines have also reached out to the SEO industry, and are frequent sponsors and guests at SEO conferences, webchats, and seminars. Major search engines provide information and guidelines to help with website optimization.[18][19] Google has a Sitemaps program to help webmasters learn if Google is having any problems indexing their website and also provides data on Google traffic to the website.[20] Bing Webmaster Tools provides a way for webmasters to submit a sitemap and web feeds, allows users to determine the "crawl rate", and track the web pages index status.
In 2007, Google announced a campaign against paid links that transfer PageRank.[30] On June 15, 2009, Google disclosed that they had taken measures to mitigate the effects of PageRank sculpting by use of the nofollow attribute on links. Matt Cutts, a well-known software engineer at Google, announced that Google Bot would no longer treat any nofollow links, in the same way, to prevent SEO service providers from using nofollow for PageRank sculpting.[31] As a result of this change the usage of nofollow led to evaporation of PageRank. In order to avoid the above, SEO engineers developed alternative techniques that replace nofollowed tags with obfuscated JavaScript and thus permit PageRank sculpting. Additionally several solutions have been suggested that include the usage of iframes, Flash and JavaScript.[32]

SEM search placements include an “Ad” designation. SEO does not. Search results that appear as a result of SEM or SEO look different on SERPs. Paid ads that receive placement through SEM tactics are often identified as an ad (e.g., by an icon appearing next to the placement), whereas the search results that appear as a result of organic SEO are not marked in such manner.

Unfortunately, Google has stopped delivering a lot of the information about what people are searching for to analytics providers. Google does make some of this data available in their free Webmaster Tools interface (if you haven’t set up an account, this is a very valuable SEO tool both for unearthing search query data and for diagnosing various technical SEO issues).
If you are just starting out, don’t think you can fool Google about everything all the time. Google has VERY probably seen your tactics before. So, it’s best to keep your plan simple. GET RELEVANT. GET REPUTABLE. Aim for a healthy, satisfying visitor experience. If you are just starting out – you may as well learn how to do it within Google’s Webmaster Guidelines first. Make a decision, early, if you are going to follow Google’s guidelines, or not, and stick to it. Don’t be caught in the middle with an important project. Do not always follow the herd.
Thick & Unique Content – There is no magic number in terms of word count, and if you have a few pages of content on your site with a handful to a couple hundred words you won’t be falling out of Google’s good graces, but in general recent Panda updates in particular favor longer, unique content. If you have a large number (think thousands) of extremely short (50-200 words of content) pages or lots of duplicated content where nothing changes but the page’s title tag and say a line of text, that could get you in trouble. Look at the entirety of your site: are a large percentage of your pages thin, duplicated and low value? If so, try to identify a way to “thicken” those pages, or check your analytics to see how much traffic they’re getting, and simply exclude them (using a noindex meta tag) from search results to keep from having it appear to Google that you’re trying to flood their index with lots of low value pages in an attempt to have them rank.
to avoid throwing link equity away, you might create HIGH-LEVEL IN-DEPTH TOPIC PAGES on your site and redirect (or use canonical redirects) any related expired content that HAVE INCOMING BACKLINKS, to this topic page (and keep it updated, folding content from old pages, where relevant and there is traffic opportunity, to create TOPIC pages that are focused on the customer e.g. information pages)

So what are the rules of thumb here? First and foremost, it’s very important that your content is easy to read. Of course, you should use your keywords in your text, but don’t stuff your keywords in almost every sentence. In general, if 1 or 2% of all words of your copy, is your keyword, then you’re not overdoing it. Make sure your keywords are well-distributed throughout your text. Don’t put all your keywords in the first paragraph thinking you’re done with that part of the optimization. Naturally spread the keywords throughout your page or post. Use your keywords in a subheading or a couple of subheadings, depending on the length of your page or post. And use the keyword in your page title, first paragraph and your meta description. You can find all of these recommendations in the SEO analysis of Yoast SEO.

But essentially the idea there is that this is a good representative of the the content from your website and that’s all that we would show to users on the other hand if someone is specifically looking for let’s say dental bridges in Dublin then we’d be able to show the appropriate clinic that you have on your website that matches that a little bit better so we’d know dental bridges is something that you have a lot on your website and Dublin is something that’s unique to this specific page so we’d be able to pull that out and to show that to the user like that so from a pure content duplication point of view that’s not really something I totally worry about.

Baseline ranking assessment. You need to understand where you are now in order to accurately assess your future rankings. Keep a simple Excel sheet to start the process. Check weekly to begin. As you get more comfortable, check every 30 to 45 days. You should see improvements in website traffic, a key indicator of progress for your keywords. Some optimizers will say that rankings are dead. Yes, traffic and conversions are more important, but we use rankings as an indicator.